<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
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  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
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<body>
  

<script>
 let score = prompt('请输入你的分数')
 if (score>=90 ) alert('A')
  else if (score>=80 && score<90) alert('B')
  else if (score>=70 && score<80) alert('C')
  else if (score>=60 && score<70) alert('D')
  else alert('E')

 
</script>
</body>
</html>